How can I call Google Charts API from UrlFetch service in Google App Script? -

i'm trying write sort of proxy able query google spreadsheet google chart api without giving rights directly spreadsheet people accessing visualization.

in order that, want replace calls like

var query = new google.visualization.query('http://spreadsheets.google.com/tq?key=the_key'); query.send(handlequeryresponse); 

by calls of apps script proxy (with jsonp).

i wrote proxy following : (i'll add later option encapsulate result in function - jsonp)

function doget(e) {   return contentservice     .createtextoutput(       urlfetchapp         .fetch("http://spreadsheets.google.com/tq?tq="+e.parameter.q+"&key="+e.parameter.key))         .setmimetype(contentservice.mimetype.json); } 

when trying response, obtain error : google.visualization.query.setresponse({"version":"0.6","status":"error","errors":[{"reason":"user_not_authenticated","message":"user not signed in","detailed_message":"\u003ca target=\u0022_blank\u0022 href=\u0022https://spreadsheets.google.com/spreadsheet/\u0022\u003esign in\u003c/a\u003e"}]});

like if user not authenticated. think it's weird because script deployed web app executed user, has rights on spreadsheet. guess must use oauth, don't know how authenticate query way.

so question : how authenticate query apps script access data access rights defined when deploying web app ?

see urlfetch docs. missing oauth stuff. way doing work public ss.